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IanBarber
12-Jul-2017, 14:04
Ive been using a spirit type thermometer but I find it difficult to read the small scale.

Can any tell me if this type of Weston thermometer is any good for chemical temperature measurement

167189

domaz
12-Jul-2017, 14:14
In my experience dial thermometers are just not very accurate. If you can't read a conventional spirit thermometer you might consider getting a digital thermometer with and LCD and probe.

xkaes
12-Jul-2017, 14:16
You can get a pretty good check on the accuracy by comparing it to another thermometer, such as a household mercury thermometer, an aquarium thermometer of a household/furnace thermometer. A few of these thermometers have a nut around the shaft to allow adjustment/correction.

But if it is too difficult to read, you can either buy one with a larger face or get a digital one with a bright readout.

Charlie Strack
12-Jul-2017, 15:23
The original Weston thermometers were specified as accurate to within 1/2 degree F. I've regularly used them. Now I have a thermocouple cooking thermometer that I could use to check the Weston thermometers, but the cooking thermometer was $180 US. I would not use it in chemistry, through, since I'm not sure of the metal it uses-I would check against cold and hot water.

LabRat
12-Jul-2017, 15:59
Go to the hardware store or supermarket and buy a digital thermometer with a stainless steel stem, and water resistant construction (it will cost $10-$15)... Measures 10ths of a degree, responds quickly to changes, has a memory hold, reads F or C, and can even read temp differences in a thermocline in your solutions...

Good, cheap investment, and you can find contractor grade units for a little more, but still the same basic circuit...

Steve K

Luis-F-S
12-Jul-2017, 16:17
I find mine more than accurate enough for B&W use

Jerry Bodine
12-Jul-2017, 16:42
My step-daughter asked me what I'd like for Fathers' Day a while ago. I responded "What would you get for the guy who has everything (hint: the answer is NOT penicillin)?" After thinking a bit and not wanting to break her bank account, I told her I could use another thermometer in the darkroom - a digital stem-type - as I have a couple of non-adjustable Weston dial-types with corrections taped on them (compared to my Kodak Process Thermometer). She found an acceptable one via Amazon ($10-15) that I blessed before she purchased - it reads F & C, responds quickly and holds the reading until turned off. And it also agrees with my Kodak one. Now I'm no longer like the guy with two watches who never knows what time it is, because the watches never agree. I don't plan to continue using the Westons.

Jim Jones
12-Jul-2017, 16:49
A mercury or spirit thermometer is reliably accurate as long as it is unbroken and there is no gap in the mercury or spirit column. I've had dial darkroom thermometers become inaccurate. Sometimes this can be fixed, sometimes not. They are convenient and reliable enough if frequently checked against a good mercury or spirit thermometer.

Bob Salomon
12-Jul-2017, 16:49
My step-daughter asked me what I'd like for Fathers' Day a while ago. I responded "What would you get for the guy who has everything (hint: the answer is NOT penicillin)?" After thinking a bit and not wanting to break her bank account, I told her I could use another thermometer in the darkroom - a digital stem-type - as I have a couple of non-adjustable Weston dial-types with corrections taped on them (compared to my Kodak Process Thermometer). She found an acceptable one via Amazon ($10-15) that I blessed before she purchased - it reads F & C, responds quickly and holds the reading until turned off. And it also agrees with my Kodak one. Now I'm no longer like the guy with two watches who never knows what time it is, because the watches never agree. I don't plan to continue using the Westons.
Then you obviously need a third watch!

xkaes
12-Jul-2017, 17:37
I've used a lot of thermometers over time -- of various types. My most frequently used is a Weston-metallic-type, but with a bigger scale for easy reading. I have a great Unicolor Precision, mercury thermometer. More accurate, in terms of fine-tuned scale -- but who needs it? It is still VERY difficult to see the TINY mercury line!!!

No matter what thermometer you use -- it will be inaccurate. But the important thing is that it is consistent. So maybe it is 1 or 2 degrees high or low from reality. Who carses? If you run tests using your thermometer (NOT tests OF the themometer), then it will be OK. Just make sure you use the same thermometer. If a "process" says 90 degrees +/- 1/4 degree, run tests using your gear and get it right -- whatever the temperature readout is on your thermometer.

Jerry Bodine
12-Jul-2017, 17:47
Then you obviously need a third watch!

And simply average them, or get several and develop an algorithm for a programmable HP calculator (they run on RPN - Reverse Polish Notation? Just kidding, of course. :D

Robert Bowring
13-Jul-2017, 06:27
I have used a Weston adjustable dial thermometer for a long time and find it to be very reliable. I check it regularly against my Unicolor Precision mercury thermometer and adjust it if necessary. Works very well.

Richard Wasserman
13-Jul-2017, 06:45
If you use the same thermometer all the time and adjust your process accordingly, I don't see why the thermometer needs to be perfectly accurate, close enough seems OK to me, as long as it reads the same all the time. I'm thinking B&W

Harold_4074
14-Jul-2017, 10:38
About three years ago, I bought a new Weston thermometer to replace the little 1" dial thermometer that I had always used. It was a while (months) before I put it to use, and discovered that while it was quite accurate (against a Kodak Process Thermometer) it would sometimes stick. Tapping the face would give a true reading, so I considered the merits of returning it. But then I realized that I sort of instinctively tap any dial-type gauge (pressure, temperature, voltage...) so maybe knowing that I have to tap it is better than getting a "good" one and just assuming that I won't.

Incidentally, one of the better arguments for electronic thermometers is that slightly bending the step will not change the calibration. This happened to my old thermometer, and the low reading (about 1-1/2 scale divisions) was enough to ruin some pictures until I figured it out...

Whatever style one uses, having a liquid-in-glass thermometer readable to a degree (F) or less and reserved as a reference is a very, very good idea---both electronic and mechanical thermometers can go bad slowly.